1. Field of the Invention
The present invention relates to a toilet bar suitable for cleansing. In particular, it relates to a toilet bar which has an ordered, layered (or multilayered) microstructure and whose continuous phase is iridescent and contains specific ethoxylated alcohols.
2. The Related Art
Iridescent, opalescent or pearly solid and liquid cosmetic products are known in the cosmetic industry and are designed to appear attractive to consumers. Iridescent, opalescent or pearly product descriptions are often used interchangeably and generally convey the fact that iridescence is a characteristic of the product. Iridescence is defined as an optical phenomenon whereby light is scattered between two ordered layers. The resulting colors and their intensity are seen to vary as a function of detection angle or observer position with respect to the article. Iridescence in a given product can arise from the continuous phase, from the dispersed phase such as from iridescent pigments or discrete particles blended into the product, or from some combination thereof.
U.S. Pat. No. 6,946,124 issued to Arnaud-Sebillotte et al. on Sep. 20, 2005 discloses an iridescent cosmetic composition that contains surfactant(s) and polymer particles in a specific diameter range. U.S. Patent Publication Nos. 2003/0021817 and 2003/0053979 both to Arnaud-Sebillotte et al. and published on Jan. 30, 2003 and Mar. 20, 2003 respectively, disclose other iridescent cosmetic compositions that contain polymer particles in a specific diameter range.
PCT publication no. WO 91/09106 to El-Nokaly et al. published on Jun. 27, 1991 discloses extruded toilet bars made with polymeric lyotropic liquid crystals that confer iridescent properties to the bars.
PCT publication no. WO 95/03392 to Dumas et al. published on Feb. 2, 1995 discloses the use of work energy of mixing to render specific soap bars transparent.
Strey at al. “Freeze Fracture Electron Microscopy of Dilute Lamellar and Anomalous Isotropic (L3) Phases”, Langmuir, Vol. 6, pp. 1635-1639 (1990); discloses an investigation of a binary water-ethoxylated alcohol (EA) C12E5 system for forming a lamellar phase.
U.S. Pat. No. 3,789,011 to Tanaka, issued on Jan. 29, 1974 discloses a non-extruded melt cast transparent soap bar having pearlescent qualities that are provided by a dispersed phase composed of various inorganic materials or pigments.
U.S. Pat. No. 6,482,782 to Kim, issued on Nov. 19, 2002 also discloses a pearlescent non-extruded, melt cast soap bar containing in its dispersed phase coated micaceous powder.
Surprisingly, it was discovered that specific ethoxylated alcohols could produce iridescent continuous phase soap bars within specific formulation constraints and within a wide process window provided an ordered layered structure was present. Such process conditions are preferably characterized by 1) selective binding of free water to soap and 2) intensive mass shearing conditions to enhance the ordered layered structure. Such mass shearing conditions are believed to generate high extensional forces and can be accomplished by moving a perforated plate through the soap mass. In a preferred embodiment, iridescence of the bar is enhanced by sequential mixing which facilitates the preferential binding of water to the soap as opposed to water binding to the ethoxylated alcohol (or other hydrophilic components). In other words, all available sites of soap that can bind to water are saturated with water prior to adding the ethoxylated alcohol. This can also be expressed as the ratio of the total bound water to water that is bound to the soap being greater than 1.0. Bound water is herein defined as that water that is unavailable for binding to or solvating other hydrophilic materials formulated into the inventive soap bar such as but not limited to the ethoxylated alcohol. In a further preferred embodiment, additional shear is provided to the soap mass during the extrusion stage from e.g. a plastometer, followed by an equilibration stage after soap bar compression so as to produce a more intense iridescent effect.
The phenomena of iridescence in the continuous phase of the inventive soap bar is characterised as a blue hue whose intensity depends on the viewing angle. The perceived intensity of the blue hue also depends on the color and illumination of the surroundings. The inventive bar appearance is contrasted with the optical effects produced via the addition of iridescent pigments or particles (i.e. the dispersed phase) to prior art bars. Such dispersed phase particles produce both a qualitative and quantitative different optical appearance to that generated by the inventive continuous phase iridescent material. The degree of iridescence generated in the inventive soap bar (i.e. its continuous phase) was seen to vary as a function of free water content, the degree of alcohol ethoxylation, the ethoxylated alcohol concentration, and the ratio of alcohol concentration to ethoxylation degree and is discussed in further detail below. Irridescent, reflective, colored or other particles or blends thereof may be optionally added to the inventive soap bar.